1. Can you identify a portal system in the renal circulation? The glomerulus is the site of the portal circulation in the kidneys. The afferent arteriole enters the glomerulus and ultrafiltration of blood occurs here while the rest of the blood is carried in the efferent arteriole to the venules. Thus blood is carried into the glomerulus, as well as out of the glomerulus by the arterioles.
2. What do you predict would be the effect of ACE inhibitors on the tubular reabsorption of water by the kidneys? ACE inhibitors cause failure of the action of angiotensin to cause aldosterone secretion. Aldosterone causes tubular reabsorption of salt and water. Thus ACE inhibitors cause loss of salt and water from the body, resulting in decrease in blood pressure
3. What would you expect the value of renal clearance of glucose to be in a healthy individual?why? All of the glucose that comes to the kidney is saved and leaves the kidney in the plasma and that no glucose is excreted into the urine. The clearance of glucose is therefore 0 ml/min as no plasma has its glucose removed as it passes through the kidney. This would be true for any substance that is completely reabsorbed.
4. How would glomerular filtration rate be affected by kwashiorkor? In kwarshiorkar there is reduced plasma proteins, particularly albumin. This causes reduced plasma oncotic pressure, which thus is unable to retain fluid, and results in increased GFR
5. Drugs called renin inhibitors are used to treat hypertension. Ezplain how they would have this effect. Rennin is an enzyme, acting on a globulin known as angiotensinogen to split it into angiotensin I. this is further split into angiotensin II. This increases the blood pressure by vasoconstriction and salt retention. Thus rennin inhibition will cause a reduction in BP 6. Some tumors of the brain, pancreas, and small intestine secete ADH. What type of water imbalance would this produce?Explain why. ADH causes water retention in the distal tubules and collecting ducts. This type of water retention occurs without salt retention, and occurs physiologically in states of dehydration. Thus causing hyposomolality
7. What protein do you think is the most important buffer in blood plasma? In erythrocytes? By far the most important buffer for maintaining acid-base balance in the blood is the carbonic-acid-bicarbonate buffer. Hemoglobin also acts as a pH buffer in the RBC. Hemoglobin protein can reversibly bind either H+ (to the protein) or O2 (to the Fe of the heme group), but that when one of these substances is bound, the other is released (as explained by the Bohr effect)
8. Explain why the respiratory and urinary system are both necessary for the bicarbonate buffer system to work effectively in the blood plasma. The lungs remove excess CO2 from the blood (helping to raise the Ph by hyperventilation; and the kidneys remove excess HCO3- from the body (helping to lower the pH).